The present invention generally relates to a method for correcting the bending of a carrier, a shaft or an axle.
The carrier in the region of each of its two ends is supported by a pair of supporting elements. Each pair of supporting elements is formed by two supporting elements. The carrier is bent due to its weight and possibly due to additional loads and/or to loading forces being applied onto the supporting elements. A counter bending force counteracting the bending is introduced into the supporting elements. Additionally, an apparatus being suitable for conducting the method is disclosed.
The invention can be applied in all cases in which a carrier is submitted to bending, and in which bending is undesired and has a negative effect. The changing or correcting of the bending or deflection of a carrier is described, i.e., a manner how to counteract bending in the sense of a controlled process. The carriers may have very different designs. The carriers may be non-moving beams. Nevertheless, it is preferred to apply the invention to rotatingly driven or rotating carriers, especially shafts with which a torque is transmitted, and axles serving to hold transverse forces. Preferred fields of application of the invention are warm and cold rolling mills, sheet metal bending machines, paper machines, reel slitting machines, calenders and similar devices. It is also possible to use the present invention in case of applying paste-like masses onto plane carrier material, which is carried out by means of rollers.
A method and an apparatus are known from the German Patent Application number DE 44 39 908 A1. A winding shaft being supported on supporting elements is used as a carrier. The plane material is winded around the carrier to form a wind lap. When the diameter of the wind lap increases, the additional load of the wind lap and the weight of the shaft cause in a deflection of the winding shaft, so that not only the winding shaft, but also the wind lap is bent. The winding shaft in the region of its two ends is supported by a pair of supporting elements. Each pair of supporting elements includes two supporting elements. Both supporting elements of the pair of supporting elements can be formed as bearings. The two bearings of one side are supported with respect to one another by a frame. A compensation device in form of a working cylinder is arranged inside the frame. Thus, the frame is designed to be moveable. The working cylinder contacts one of the two bearings, and it applies a controlling force onto the supporting element it engages. Consequently, at the other bearing a corresponding reaction force results. Both forces produce a counter bending moment which counteracts the bending of the winding shaft. A control device including a computer unit, a control line and a control element is provided to control the controlling force acting upon the winding shaft by the working cylinder. This arrangement provides a compensation device. The compensation device has a rather complicated structure, and it requires the arrangement of a special power source acting upon the working cylinder. Depending on the design of the control device and of its way of operating, the bending effect resulting form the additional load of the wind lap and/or by the loading force onto the winding shaft can be at least partially compensated by the counter bending forces being applied at the end of the shafts.
To counteract the disadvantages of the bending of shafts, it is further known to emboss the rollers. The rollers are designed in an embossed fashion, the diameter of the rollers being chosen to have twice the amount in the region of the middle of the roller than it corresponds to the bending of the roller during operation. This arrangement has a positive effect, but it requires that the rollers are exclusively operated in a small working region, in which neither the pressing forces nor the characteristics of the material to be treated substantially change. On the other hand, in case of different working conditions, it is known to produce special embossed rollers for each working condition, and to replace the rollers. This method is rather expensive since it is difficult to produce exact embosses and due to the necessary retool times.
Hydrostatic bearings are explained and described in the magazine Fluid, June 1978, pages 31-37, xe2x80x9cHydrostatische Lagerung in Papiermaschinenxe2x80x9d, Volz/Voetsch. The hydrostatic bearings spaced apart in the direction of the axis of the shaft. Thus, hydraulic single supporting elements are shown and described. The single supporting elements are individually impinged to provide counter forces in certain sections of heavy rollers, especially in paper machines. The structural and the controlling expenditure of such a hydraulic bearing including a plurality of supporting points is great.
It is therefore an object of the present invention to provide a method for correcting the bending of a shaft, an axle or another carrier, i.e. to provide the possibility of a counteracting control, that counteracts the bending of the shaft, the axle or the other carrier without the requirement of a complicated control device.
It is another object of the present invention to provide an apparatus suitable for conducting the method. The apparatus has an advantageously simple structure, and it is therefore inexpensive to use in different fields of application.
According to the present invention, this is achieved in a method for corrections the bending of a carrier by the counter bending force being derived from the weight of the carrier and possibly of the additional loads and/or the loading forces being introduced directly into the supporting elements.
The invention is based on the idea not to introduce a separately produced control force as counter bending force, but instead a counter bending force being derived from the weight and/or the loads and/or the loading forces causing the bending of the carrier. In this way, a counter bending moment is applied which acts in a direction opposite to the bending of the carrier. The named forces are directly used as counter bending forces. The counter bending force is formed by the sum of the forces causing the bending. In this way, the advantageous effect is achieved that, due to a change of the loads and/or the loading forces, the corresponding counter bending force also changes, and it adapts automatically, so that a complicated control device is not required. The force being introduced as counter bending force can be also changed to consciously compensate the bending only partially, or to overcompensate the bending. The counter bending force is directly derived from the corresponding load of the carrier. A separate power source and separate force transmitter are not required. Since the value of the counter bending force depends directly proportionally form the loads and/or loading forces directly or indirectly loading the carrier, controlling is not necessary to eliminate bending of the carrier in case of different loads and/or loading forces. This is also true for non-symmetric loads and/or loading forces, i.e. in case of forces differently acting on the different sides of the carrier.
The loading force may be introduced into both supporting elements with a distance to the supporting elements of each pair of supporting elements. By this axial distance, the ratio is advantageously used. Not only a loading force is applied, but at the same time, a counter bending moment. The counter bending forces result from the relative distances between their places of application of the forces with respect to one another and from the loading force.
The apparatus for conducting the method includes a rigid frame being arranged in the region of each end of the carrier. Each rigid frame includes a pair of supporting elements and a place of application for the introduction of the loading forces and, respectively, a place of application to bear up the counter bending force resulting from the weight and possibly from the additional loads and/or the loading forces into the supporting elements. The rigid frame is an essential structural element of the apparatus. In any case, the rigid frame is arranged in the region of each end of the carrier, and it is supported on the ends of the carrier. The frame is not additionally supported. It serves to introduce the loading force or to bear up the overall force consisting of the weight of the carrier, a possible supporting load or any other loads. This arrangement ensures that an automatic adaptation in case of the overall force changing occurs.
The place of application for the introduction of the loading forces is axially spaced apart from the pair of supporting elements. Consequently, the loading force is turned into a counter bending force being directed in opposite direction to the bending of the carrier. The pair of supporting elements is designed as two spaced apart bearings to support the carrier being designed as a shaft or as an axle. This means, that both bearings support the shaft or the axle, and on the other hand, they are supported in the rigid frame being exclusively loaded by the loading forces.
The axial distance between the two supporting elements or bearings of each pair of supporting elements may be adjustable. Such a design makes sense to apply, for example, small loading forces, and to nevertheless produce a sufficient counter bending moment being sufficient to eliminate the bending of the shaft due to the ratio. In this case, one of the supporting elements or bearings of each pair of supporting elements is designed as a fixed bearing, and the other supporting element or bearing is designed as a movable bearing. It is desirable to locate the moveable bearing between the fixed bearing and the place of application for the introduction of the loading force.
It is also possible that the place of application for the introduction of the loading force on the frame is axially adjustable. In this way, the value of the counter bending forces and of the counter bending moments, respectively, can be changed in a simple manor. The place of application for the introduction of the loading force on the frame may be also designed as a bearing. The design as a bearing has the advantage that the direction of the loading force can be changed, and in this way an automatic adaptation by applying the counter bending moments occurs. Such a case occurs, for example, when two rollers are pressed against one another, the axes of the rollers being arranged horizontally adjacent. The direction of the loading force can also change during the operation of the apparatus. An automatic adaptation also occurs in this case.
Mechanical, electrical or fluid actuated means may be provided for the adjustment of the bearings. Especially, hydraulic or pneumatic cylinders may be arranged as such means. These means are exclusively provided to adjust the bearings, and not to adjust the general application of the loading force.